I was wondering if there is an easy and quick way to tell if I am missing a file
in multiple directories and then make a list and output it to a text file.

The situation is I'm running XBMC on my Ras Pi and NAS. Not all of my films (and music) have folder/cover art.
Rather than go through each dir one by one and check. I thought that there must be any easy way to check
this with the terminal command or a bash script.

Something like -
Look at all these dirs (and sub dirs), do they contain the file "folder.jpg"
if not, then name the dir it's missing from and make a list in
a text file for me.

I've taken a quick look on google and I've seen a few that look promising (but they have a bunch of commands
and operators and it quickly begins to look like Klingon).